Through an offseason of notable change, the Philadelphia Eagles' deep and talented offensive line remained a constant. DeSean Jackson might be gone, but Chip Kelly's offense maintained the big, ugly engine that made all his innovation possible. And while the line is built more on collective strength, Lane Johnson's looming absence is worth noting entering training camp.

Johnson faces a four-game suspension for testing positive for performance-enhancing drugs, according to the Philadelphia Daily News. There has been no official comment from the Eagles or the NFL.

The Eagles' first-round pick in the 2013 NFL draft, Johnson started all 16 games at right tackle last season and ranked No. 11 among all offensive tackles for his abilities as a run blocker, according to Pro Football Focus. He showed improvement in the second half of last season and became an integral part of the Eagles' running game.

Johnson looked the part of a raw prospect in pass protection, but showed the athleticism and promise that made him the No. 4 overall pick in the 2013 draft. A former tight end, Johnson was noticeably further ahead as a run-blocker than as a pass-blocker.

Johnson's four-game suspension will temporarily halt the momentum he built late last season and create a potential need for depth along the line. Swing lineman Allen Barbre is the most likely choice to play in Johnson's absence, which then creates a need for experienced depth elsewhere.

General manager Howie Roseman could enter the free agency market with an eye toward signing a veteran interior lineman. His in-house options for backups include tackles Dennis Kelly, Matt Tobin and Andrew Gardner and guards Karim Barton and Donald Hawkins. Injuries also pushed veteran guard Todd Herremans into starting duties at right tackle in 2012.